1. Field of the Invention
A transposing apparatus whereby each sound produced is uniformly changed in pitch from that normally associated with the digital struck.
2. Description of the Prior Art
With an organ tuned in the conventional equitempered scale, a melody written in a particular key may have all its tones uniformly raised or lowered by a pitch changing mechanism; it will be recognized in that case as being the same melody, pitched higher or lower.
When a singer or instrumentalist is accompanied by an organ or piano, he often wishes the accompaniment to be pitched higher or lower than the music is written, to better match the range of his voice or instrument. This can be accomplished, without changing the fingering of the music as written, by means of a pitch changing switch which alters the connections between the tone generators and the digitals which actuate them. By changing the position of the switch, the absolute pitch of tones corresponding to the sequence of digitals may be uniformly raised by a fixed amount -- say four semitones.
If the organ is tuned in a twelve tone scale which differs somewhat from the equitempered scale, then a change of pitch may affect the way a musical composition sounds. For example, if the tone generators are tuned in the one-quarter comma meantone scale, then a composition will probably sound pleasant at some pitches and discordant at others, but it will generally be recognizable as the same composition. Pitch changing switches are still useful with such scales, which may be called approximately equitempered scales.
The most satisfactory pitch changing system is one which can be set to a standard position in which middle A has a fundamental frequency of 440 Hz, and changed therefrom to at least eleven other positions in which the pitch is changed from the standard by an integral number of semitones.
Wick, in U.S. Pat. No. 3,030,848, describes a pitch changing switch which has stationary contacts on one stationary printed circuit board which are connected to the tone generator circuits. Stationary contacts on a second stationary printed circuit board are connected to the digital switches. Between the two stationary circuit boards is a rotor.
Bode, in U.S. Pat. No. 3,023,659, describes a pitch changing system in which the pitch of only the top octave of tone generators is switched; lower octaves of tone generators are derived from the top octave by twelve chains of binary frequency dividers.
It is known that binary frequency dividers slaved to a top octave of twelve master oscillators produce a tone quality which is generally inferior to that produced by independent tone generators, but that good tone quality can be obtained by using two or more separate sets of master oscillators, each with its own set of binary frequency dividers. The great majority of musical instruments do not presently contain pitch changers, largely because of their size, expense, unreliability, and the added complexity of wiring required for their use.